Adaptive multiple sub-band common-mode RFI suppression

Details Adaptive multiple sub-band common-mode RFI suppression Adaptive multiple sub-band common-mode RFI suppression

1998-05-14

2000-04-18

Bocure, Tesfaldet

Pulse or digital communications

Receivers

Interference or noise reduction

375258, H04B 110, H04B 300

Patent

active

060524200

ABSTRACT:
A noise suppression circuit for a two-wire communications channel comprises a hybrid device, for example a hybrid transformer or circuit, for providing a differential mode signal corresponding to a differential signal received from the two-wire channel. A summing device extracts from the two-wires of the channel a common mode signal and supplies it to a noise estimation unit which derives from the common mode signal an estimate of a noise level in at least one frequency band having a bandwidth considerably narrower than an operating bandwidth for the channel. The noise estimation unit adjusts the amplitude of the noise estimate to correspond to the residual noise in the differential mode signal and subtracts it from the differential mode signal to produce a noise-suppressed output signal. A noise detection and control unit scans the operating band, identifies a frequency band having an instant highest noise level, and sets the noise estimation unit to the detected noisy band. The noise estimation unit suppresses the noise in that band. In preferred embodiments, the noise estimation unit comprises several channels, each comprising a tunable filter, a phase shifter and an amplifier, and the noise detection and control unit sets the channels, in succession, to different frequency bands in descending order of noise level. The noise detection and control unit may cross-correlate the common mode signal and the noise-suppressed output signal and adjust the amplification of the noise estimation signal to reduce residual differential mode noise substantially to zero.

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